System and Method for an Adaptive Frame Structure with Filtered OFDM

ABSTRACT

Different filtered-orthogonal frequency division multiplexing (f-OFDM) frame formats may be used to achieve the spectrum flexibility. F-OFDM waveforms are generated by applying a pulse shaping digital filter to an orthogonal frequency division multiplexed (OFDM) signal. Different frame formats may be used to carry different traffic types as well as to adapt to characteristics of the channel, transmitter, receiver, or serving cell. The different frame formats may utilize different sub-carrier (SC) spacings and/or cyclic prefix (CP) lengths. In some embodiments, the different frame formats also utilize different symbol durations and/or transmission time interval (TTI) lengths.

This patent application claims priority to U.S. Provisional Application No. 62/140,995, filed on Mar. 31, 2015 and entitled “System and Method for an Adaptive Frame Structure with Filtered OFDM,” which is hereby incorporated by reference herein as if reproduced in its entirety.

TECHNICAL FIELD

The present invention relates to a system and method for wireless communications, and, in particular embodiments, to a system and method for an adaptive frame structure with filtered orthogonal frequency division multiplexing (OFDM).

BACKGROUND

As mobile devices are increasingly used to access streaming video, mobile gaming, and other assorted services, next-generation wireless networks may need to support diverse traffic types while also satisfying overall network and channel performance requirements. The different traffic types may have different characteristics, including different quality of service (QoS) requirements (e.g., latency, packet loss, jitter, etc.). Accordingly, techniques for efficiently communicating diverse traffic types over resources of a wireless network are needed to enable next-generation wireless networks to satisfy the demands of tomorrow.

SUMMARY OF THE INVENTION

Technical advantages are generally achieved, by embodiments of this disclosure which describe a system and method for an adaptive frame structure with filtered OFDM.

In accordance with an embodiment, a method for transmitting signals in a wireless network is provided. In this example, the method includes transmitting a first filtered-orthogonal frequency division multiplexing (f-OFDM) signal, and transmitting a second f-OFDM signal. The first f-OFDM signal and the second f-OFDM signal are communicated in accordance with different sub-carrier spacings than one another. An apparatus for performing this method is also provided.

In accordance with another embodiment, a method for receiving signals in a wireless network is provided. In this example, the method includes receiving a first filtered-orthogonal frequency division multiplexing (f-OFDM) signal, and receiving a second f-OFDM signal. The first f-OFDM signal and the second f-OFDM signal are communicated in accordance with different sub-carrier spacings than one another. An apparatus for performing this method is also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates a diagram of an embodiment wireless network;

FIG. 2 illustrates a diagram of an embodiment filtered-orthogonal frequency division multiplexing (f-OFDM) configuration;

FIG. 3 illustrates a diagram of another embodiment f-OFDM configuration;

FIG. 4 illustrates a flowchart of an embodiment method for transmitting f-OFDM signals having different frame formats;

FIG. 5 illustrates a flowchart of another embodiment method for transmitting f-OFDM signals having different frame formats;

FIG. 6 illustrates a flowchart of an embodiment method for receiving f-OFDM signals having different frame formats;

FIG. 7 illustrates a diagram of an embodiment f-OFDM configuration;

FIG. 8 illustrates a diagram of another embodiment f-OFDM configuration;

FIG. 9 illustrates a diagram of yet another embodiment f-OFDM configuration;

FIG. 10 illustrates a flowchart of an embodiment method for configuring a downlink f-OFDM frame;

FIG. 11 illustrates a flowchart of an embodiment method for modifying downlink f-OFDM parameters;

FIG. 12 illustrates a flowchart of another embodiment method for modifying downlink f-OFDM parameters;

FIG. 13 illustrates a flowchart of yet another embodiment method for modifying downlink f-OFDM parameters;

FIG. 14 illustrates a flowchart of an embodiment method for configuring an uplink f-OFDM frame;

FIG. 15 illustrates a flowchart of another embodiment method for transmitting an uplink f-OFDM frame in accordance with uplink f-OFDM parameters;

FIG. 16 illustrates a diagram of yet another embodiment f-OFDM configuration;

FIG. 17 illustrates a diagram of yet another embodiment f-OFDM configuration;

FIG. 18 illustrates a diagram of yet another embodiment f-OFDM configuration;

FIG. 19 illustrates a diagram of yet another embodiment f-OFDM configuration;

FIG. 20 illustrates an example of an intra-f-OFDM adaptive TTI configuration;

FIG. 21 illustrates a diagram of an embodiment communications device; and

FIG. 22 illustrates a diagram of an embodiment computing platform.

Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The structure, manufacture and use of the embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

Aspects of this disclosure utilize different filtered-orthogonal frequency division multiplexing (f-OFDM) frame formats to achieve the spectrum flexibility needed to support diverse traffic types in next-generation wireless networks. F-OFDM waveforms are generated by applying a pulse shaping digital filter to an orthogonal frequency division multiplexed (OFDM) signal. Embodiments of this disclosure use different frame formats to carry different traffic types as well as to adapt to characteristics of the channel, transmitter, receiver, or serving cell. The different frame formats utilize different sub-carrier (SC) spacings and/or cyclic prefix (CP) lengths. In some embodiments, the different frame formats also utilize different symbol durations and/or transmission time interval (TTI) lengths. As referred to herein, the terms “frame format” and “frame structure configuration” are used interchangeably.

As mentioned above, using different frame formats to communicate traffic may provide significant spectrum flexibility, as using different combinations of CP lengths, sub-carrier spacings, symbol durations, and TTI lengths has performance ramifications, e.g., latency, spectral efficiency, etc. In some embodiments, f-OFDM signals are assigned to different frame formats. The assignment may be based on any criteria, e.g., a characteristic of data carried in the respective f-OFDM signals, a characteristic of a wireless channel over which the f-OFDM signal is transmitted, a characteristic of a transmitter assigned to transmit the f-OFDM signal, a characteristic of a receiver assigned to receive the f-OFDM signal, etc. The assignment of frame formats to f-OFDM signals may be achieved in a variety of ways. In some embodiments, the frame formats are mapped to network resources, and the f-OFDM signals are transmitted in the network resource based on that mapping to achieve the appropriate frame format assignment. In one example, different frame formats are mapped to different frequency sub-bands, and the f-OFDM signals are assigned to whichever frequency sub-band is mapped to the appropriate frame format. In another example, different frame formats are mapped to different time periods, and the f-OFDM signals are assigned to whichever time period has the appropriate frame format. Frame formats having different parameters may be in the same frequency sub-band or different frequency sub-bands. In other embodiments, the frame formats may be directly assigned to the f-OFDM signals independent of resource scheduling. In such embodiments, the assigned frame format may be used to transmit the f-OFDM signal over whichever resources are assigned to carry the f-OFDM signal. This may achieve greater network flexibility, while potentially having higher overhead requirements by virtue of having to persistently coordinate which frame formats are being applied to which network resources. These and other aspects are described in further detail below.

FIG. 1 illustrates a network 100 for communicating data. The network 100 includes an access point (AP) 110 having a coverage area 101, a plurality of mobile devices 120, and a backhaul network 130. The AP 110 may be any component capable of providing wireless access by, among other things, establishing uplink (dashed line) and/or downlink (dotted line) connections with the mobile devices 120, such as a base station, an evolved Node B (eNB), a femtocell, and other wirelessly enabled devices. The mobile devices 120 may be any component capable of establishing a wireless connection with the AP 110, such as a mobile station (STA), a user equipment (UE), or other wirelessly enabled devices. The backhaul network 130 may be any component or collection of components that allow data to be exchanged between the AP 110 and a remote end. In some embodiments, there may be multiple such networks, and/or the network may comprise various other wireless devices, such as relays, low power nodes, etc.

FIG. 2 illustrates a diagram of an embodiment filtered-orthogonal frequency division multiplexing (f-OFDM) configuration 200. As shown, the f-OFDM configuration 200 comprises frequency sub-bands 210, 220, 230, 240 over which different frame formats 201-204 are transmitted. Each of the different frame formats 201-204 has a different combination of frame parameters, e.g., CP-lengths, SC spacing, symbol duration, TTI length, etc. In some embodiments, different frame formats are assigned to different frequency sub-bands. In this example, the sub-band 210 is assigned the frame format 201, while the sub-band 220 is assigned the frame format 202. In other embodiments, different frame formats are assigned to be communicated at different time periods in the same frequency sub-band. In this example, the frame formats 201, 202 are assigned in a time division multiplexed (TDM) fashion. While an alternating pattern of two frame formats (i.e., the frame formats 201, 202) are depicted as being communicated over the sub-band 230, it should be appreciated that any pattern of frame formats, and any number of different frame formats, can be assigned to a frequency sub-band. In other embodiments, different frame formats may be communicated over different sub-carriers of the same frequency sub-band. In this example, the frame formats 203, 204 are communicated over different sub-carriers of the frequency sub-band 240. The bandwidths of the frequency sub-bands 210, 220, 230 and 240 can be changed over time. Other examples are also possible.

In some embodiments, frame formats can be assigned to f-OFDM signals communicated over one or more frequency sub-bands. FIG. 3 illustrates a diagram of another embodiment f-OFDM configuration 300. As shown, the f-OFDM configuration 300 comprises frequency sub-bands 310, 320, 330 over which different frame formats 301-309 are communicated. Each of the different frame formats 301-309 has a different combination of frame parameters, e.g., CP-lengths, SC spacings, symbol durations, TTI lengths, etc. In this example, the frequency sub-band 320 is assigned a default frame format 305. The frame format 305 may have a standard set of frame parameters (e.g., CP-length, SC-spacing, symbol duration, etc.) that is known by mobile devices. The default frame format 305 can be transmitted continuously in time or it can be transmitted periodically (e.g. “Config 1” in FIG. 7). This may allow mobile devices entering the wireless network to receive signals in the frequency sub-band 320. The frequency sub-band 320 may be used to assign frame formats to the frequency sub-band 310, as well as to assign frame formats to the frequency sub-band 330. Notably, dynamically assigning frame formats to the frequency sub-band 310 may allow a different frame format to be assigned to each f-OFDM signal on a frame-by-frame basis. In this example, the frame format 301 is assigned to a first f-OFDM signal communicated over the frequency sub-band 310, the frame format 302 is assigned to a second f-OFDM signal communicated over the frequency sub-band 310, the frame format 303 is assigned to a third f-OFDM signal communicated over the frequency sub-band 310, and the frame format 304 is assigned to a forth f-OFDM signal communicated over the frequency sub-band 310. The bandwidths of frequency sub-bands 310, 320 and 330 can be changed over time.

Semi-static configuration of frame formats in the frequency sub-band 330 may allow different frame formats to be assigned to different semi-static allocation periods 331, 332. Semi-static configuration of frame formats may generate less overhead than dynamic configuration of frame formats. In this example, the frame format 302 is assigned to the semi-static allocation period 331, and the frame format 309 is assigned to the semi-static allocation period 332.

FIG. 4 illustrates an embodiment method 400 for transmitting f-OFDM signals having different frame formats, as may be performed by a transmitter. As shown, the method 400 begins at step 410, where the transmitter transmits a first f-OFDM signal. Next, the method 400 proceeds to step 420, where the transmitter transmits a second f-OFDM signal. Symbols carried by the second f-OFDM signal have a different CP-length than symbols carried by the first f-OFDM signal. Additionally, the second f-OFDM signal is communicated over sub-carriers having a different sub-carrier spacing than the first f-OFDM signal.

In some embodiments, different frame formats are assigned to different f-OFDM signals. FIG. 5 illustrates another embodiment method 500 for transmitting f-OFDM signals having different frame formats, as may be performed by a transmitter. As shown, the method 500 begins at step 510, where the transmitter configures different frame formats to f-OFDM subbands based on one or more criteria. Next, the method 500 proceeds to step 520, where the transmitter transmits the f-OFDM signals in accordance with the assigned frame formats.

The criteria used to make the frame format assignments may include various characteristics associated with the signal transmission. In one example, the criteria includes a characteristic of data carried in the respective f-OFDM signals, e.g., a latency requirement, a delay tolerance requirement, a traffic type, a service type, etc. In another example, the criteria includes a characteristic of a wireless channel over which the f-OFDM signals are transmitted, e.g., multipath delay characteristic, a path loss, etc. In yet another example, the criteria includes a characteristic of the transmitter, e.g., a serving region size, etc. In yet another example, the criteria includes a characteristic of the receiver assigned to receive the f-OFDM signal, e.g., a mobility speed of the receiver. The criteria may also include a combination of the above-mentioned characteristics.

In some embodiments, frames having different frame formats are received by a single receiver. FIG. 6 illustrates an embodiment method 600 for receiving f-OFDM signals having different frame formats, as may be performed by a receiver. As shown, the method 600 begins at step 610, where the receiver receives a first f-OFDM signal. Next, the method 600 proceeds to step 620, where the receiver receives a second f-OFDM signal carrying symbols having a different CP-length than symbols carried by the first f-OFDM signal, as well as being communicated over sub-carriers having a different sub-carrier spacing than the first f-OFDM signal.

Current adaptive TTI design for 5G only works with the same subcarrier spacing and symbol duration. Various embodiments relate to frame structure design in the 5G air interface are provided. Embodiments provide a system and method for an adaptive and flexible frame structure (e.g., subcarrier spacing, symbol prefix/suffix, TTI length, etc.) in the same system bandwidth to work in filtered OFDM. Embodiments provide an adaptive frame structure (in which TTI is only one element, and subcarrier spacing and symbol prefix/suffix duration are others) that can coexist when combined with filtered OFDM in the same system bandwidth. Embodiments provide a more flexible solution to meet the diverse environment and traffic types of 5G systems due to the ability to accommodate different frame structure parameters, while at the same time enabling mobile devices to access such system easily.

FIG. 7 illustrates examples of frame structure configurations, which include subcarrier spacing, total symbol duration, symbol prefix/suffix configuration, and TTI length. As illustrated in FIG. 7, Configuration 1 is a default configuration. Configuration 2 is a configuration for low latency machine-type communication (MTC), and configuration 3 is a configuration for delay tolerant MTC. Configuration 4 is for high mobility, and configuration 5 is for broadcast service. This is applicable for both downlink and uplink.

In the intra-f-OFDM sub-band, the frame structure configurations with the same subcarrier spacing and total symbol duration can coexist. The inter-f-OFDM sub-band includes configurations with different subcarrier spacing and total symbol duration. The default frame structure occurs in predefined time-frequency resources within a default f-OFDM sub-band. This occurs at predefined periods, not necessarily all of the time. It facilitates initial access by mobile device, and may be mandatory for downlink (DL), but optional for uplink (UL). The default frame structure can be a backward compatible frame structure configuration (e.g., long-term evolution (LTE)) or a 5G default frame structure configuration. This depends on, for example, carrier frequencies.

A mechanism for adaptive frame structure with f-OFDM according to embodiments is described as follows. First, a default frame structure parameter set (configuration) is defined (e.g., default subcarrier spacing, total symbol duration, TTI length, symbol overhead such as prefix/suffix length, etc.). Next, additional frame structure parameters sets (configurations) different from the default frame structure parameter set are defined. In an embodiment, the different f-OFDM sub-band frame structure has at least a different SC spacing and total symbol duration.

Next, the default frame structure is transmitted in predefined time-frequency resources within a default f-OFDM sub-band. This is known at both the network and the mobile device (e.g., located in the bandwidth (BW) around the carrier frequency for DL). The default f-OFDM sub-band is at least the BW of the time-frequency resources occupied by the default frame structure. The default frame structure can be used for carrying any type of traffic. FIG. 8 illustrates a default f-OFDM sub-band according to an embodiment. Finally, additional frame structures in other f-OFDM sub-bands are configured on demand.

Default frame structure parameter set embodiments include a default 5G frame structure parameter set that is different from that of LTE. An LTE frame structure parameter set may include, e.g., SC (sub-carrier spacing)=15 kHz, TTI=1 ms, etc. Additional frame structure parameter set embodiments including frame structures for high speed and low speed, frame structures for a dispersive channel (e.g., outdoor) and a less dispersive channel (e.g., indoor), frame structures for different carrier frequencies, and frame structures for different traffic characteristics (e.g., latency). Table 1 lists the types of parameters that are well suited for different traffic/receivers. Table 2 lists example frame format parameters for a 7.5 kilohertz (KHz) sub-carrier spacing. Table 3 lists example frame format parameters for a 15 kilohertz (KHz) sub-carrier spacing. Table 4 lists example frame format parameters for a 30 kilohertz (KHz) sub-carrier spacing. Table 5 lists example frame format parameters for a 30 kilohertz (KHz) sub-carrier spacing. Table 6 illustrates example f-OFDM frame parameters selected from Table 1 to 5 for various configurations. The parameters may support smooth scalability of LTE in terms of subcarrier spacing (e.g., 7.5, 15, 30, 60 kHz). Embodiments include backward compatibility with the LTE basic time unit (or sampling frequency of 30.72 MHz). Various embodiments provide for narrow subcarrier spacing of 7.5 KHz along considering for device-to-device (D2D) or MTC. Various embodiments also support three types of CP for different environments, e.g., outdoor and indoor, large and small cells, e.g., mini CP (1˜2 us), normal CP (˜5 us) and extended CP (>5 us). Embodiments provide for reduced and varying CP overhead options, e.g., 1%˜10%, and short and long TTIs, e.g., able to form different frame sizes of, e.g., 0.15 ms, 1 ms, 5 ms, etc.

TABLE 1 Configuration SC-Spacing Symbol Dur. CP-Prefix TTI MTC Low small long long short Latency MTC Delay small long long medium Tolerant High Mobility large short medium medium Broadcast Services medium medium long medium

TABLE 2 Subcarrier spacing (KHz) 7.5 7.5 7.5 7.5 Useful duration T_u (us) 133.333 133.333 133.333 133.333 CP length (us) 16.667 9.54/9.44 5.57/5.18 1.82/1.76 CP length in Ts 512 293/290 171/159 56/54 (=32.55 ns) # of symbols per TTI 1 6/1 35/1  25/12 TTI ms 0.150 1 5 5 CP overhead 11.11% 6.67% 4.00% 1.33%

TABLE 3 Subcarrier spacing (KHz) 15 15 15 Useful duration T_u (us) 66.667 66.667 66.667 CP length (us) 8.333 5.2/4.7 2.31/2.28 CP length in Ts (=32.55 ns) 256 160/144 71/70 # of symbols per TTI 2 1/6 18/11 TTI (ms) 0.150 0.5 2 CP overhead 11.11% 6.67% 3.33%

TABLE 4 Subcarrier spacing (KHz) 30 30 30 30 Useful duration T_u (us) 33.333 33.333 33.333 33.333 CP length (us) 4.167  2.4/238 3.71/3.65 1.17/1.14 CP length in Ts (=32.55 ns) 128 74/73 114/112 36/35 # of symbols per TTI 4 1/6 8/1  9/20 TTI (ms) 0.150 0.250 0.333 1 CP overhead 11.11% 6.67% 10.00% 3.33%

TABLE 5 Subcarrier spacing (KHz) 60 60 60 60 Useful duration T_u (us) 16.667 16.667 16.667 16.667 CP length (us)  1.2/1.17 2.083 1.53/1.37 0.88/0.85 CP length in Ts (=32.55 ns) 37/36 64 47/42 27/26 # of symbols per TTI 4/3 8 10/1  18/1  TTI (ms) 0.125 0.150 0.200 0.333 CP overhead 6.67% 11.11% 8.33% 5.00%

TABLE 6 Symbol Dur. Configuration SC-Spacing (μs) CP-Prefix (μs) TTI (ms) MTC Low 7.5 133.333 16.667 0.15 Latency MTC Delay 7.5 133.333 16.667 1.5 Tolerant High Mobility 30 33.333 3.71/3.65 0.333 LTE Comp. 15 66.7  5.2/4.69 1

FIG. 9 is a diagram illustrating an embodiment f-OFDM configuration for supporting adaptive frame formats. In this embodiment, the 4 frame formats listed in Table 6 are communicated in 3 f-OFDM subbands of a 20 MHz spectrum. With the use of f-OFDM, the OFDM total symbol durations (cyclic prefix+useful symbol duration) corresponding to different frame structure configurations do not need to be aligned as shown in the figure. That is, non-orthogonal sets of parameters can co-exist. For example, the 30 kHz (“High mobility”) configuration has an OFDM total symbol duration of around 37 μs whereas the 15 kHz (“LTE compatible”) configuration has an OFDM total symbol duration of around 71 μs.

F-OFDM parameters can be communicated in a control channel of a default f-OFDM frame. FIG. 10 illustrates a flowchart of an embodiment method 1000 for configuring a downlink f-OFDM frame, as may be performed by a transmitter. As shown, the method 1000 begins at step 1010, where the transmitter determines f-OFDM parameters for f-OFDM signals. Thereafter, the method 1000 proceeds to step 1020, where the transmitter transmits the f-OFDM signals in accordance with the f-OFDM parameters. The DL f-OFDM parameters may include sub-band information and frame parameters. The sub-band information may include indexes of sub-bands, offsets from a reference value, or any other information associated with a sub-band. The frame parameters may identify a subcarrier spacing, a symbol duration, an overhead configuration (e.g., cyclic prefix (CP) length, etc.), a transmission time interval (TTI) duration, or any other parameter corresponding to the structure of an f-OFDM frame. The frame parameters may include indexes of a parameter set, indexes of individual parameters, or any other index, parameter, or value associated with a frame structure.

F-OFDM parameters can be communicated via higher-layer signaling. FIG. 11 illustrates a flowchart of an embodiment method 1100 for modifying downlink (DL) f-OFDM parameters, as may be performed by a transmitter. As shown, the method 1100 begins at step 1110, where the transmitter modifies DL f-OFDM parameters for DL f-OFDM signals based on criteria. The criteria may include a characteristic of data carried by the DL f-OFDM signals, a characteristic of a channel, a characteristic of the transmitter, or a characteristic of a receiver assigned to receive the DL f-OFDM signals (or a combination thereof). Thereafter, the method 1100 proceeds to step 1120, where the transmitter transmits the DL f-OFDM parameters via higher-layer signaling, e.g., radio resource control (RRC) signaling, etc. Finally, the method 1100 proceeds to step 1130, where the transmitter transmits the DL f-OFDM signals in accordance with the DL f-OFDM parameters.

F-OFDM parameters can be communicated via a default f-OFDM frame. FIG. 12 illustrates a flowchart of an embodiment method 1200 for modifying DL f-OFDM parameters, as may be performed by a transmitter. As shown, the method 1200 begins at step 1210, where the transmitter modifies DL f-OFDM parameters for DL f-OFDM signals based on criteria. Thereafter, the method 1200 proceeds to step 1220, where the transmitter transmits the modified DL f-OFDM parameters via a default DL f-OFDM frame. The f-OFDM parameters may be communicated in a control channel of the default DL f-OFDM frame. Finally, the method 1200 proceeds to step 1230, where the transmitter transmits the DL f-OFDM signals in accordance with the DL f-OFDM parameters.

F-OFDM parameters can be communicated via a previously modified f-OFDM frame. FIG. 13 illustrates a flowchart of an embodiment method 1300 for modifying DL f-OFDM parameters, as may be performed by a transmitter. As shown, the method 1300 begins at step 1310, where the transmitter modifies DL f-OFDM parameters for DL f-OFDM signals based on criteria. Thereafter, the method 1300 proceeds to step 1320, where the transmitter transmits the modified DL f-OFDM parameters via a previously modified f-OFDM frame. The DL f-OFDM parameters may be communicated in a control channel of the previously modified DL f-OFDM frame. Finally, the method 1300 proceeds to step 1330, where the transmitter transmits the DL f-OFDM signals in accordance with the newly modified DL f-OFDM parameters. This method may be particularly useful for modifications that affect mobile devices using other frame structures in other f-OFDM sub-bands, e.g., modifying other f-OFDM sub-band sizes, SC spacing, total symbol duration, and overhead duration.

It is also possible to configure uplink (UL) f-OFDM frames. FIG. 14 illustrates a flowchart of an embodiment method 1400 for configuring an uplink f-OFDM frame, as may be performed by a base station. As shown, the method 1400 begins at step 1410, where the base station determines UL f-OFDM parameters for f-OFDM signals. Thereafter, the method 1400 proceeds to step 1420, where the base station transmits the UL f-OFDM parameters to a mobile device. The UL f-OFDM parameters may be communicated via higher layer signaling or in a control channel of a downlink f-OFDM frame (e.g., default, modified, or otherwise). Finally, the method 1400 proceeds to step 1430, where the base station receives the f-OFDM signals in accordance with the UL f-OFDM parameters.

FIG. 15 illustrates a flowchart of an embodiment method 1500 for transmitting an UL f-OFDM frame, as may be performed by a mobile device. As shown, the method 1500 begins at step 1510, where the mobile device receives UL f-OFDM parameters from a base station. The UL f-OFDM parameters may be communicated via higher layer signaling or in a control channel of a downlink f-OFDM frame (e.g., default, modified, or otherwise). Thereafter, the method 1500 proceeds to step 1520, where the mobile device transmits UL f-OFDM signals in accordance with the UL f-OFDM parameters. If UL f-OFDM parameters are not pre-defined (e.g., there is no default UL f-OFDM frame), then a mobile device may obtain frame structure information from DL related signaling on initial access. If UL f-OFDM parameters are pre-defined, then a mobile device may transmit on the UL in the default frame structure without waiting for the UL f-OFDM parameters to be signaled by the base station. Thus, pre-configure the initial frame structure and f-OFDM sub-band may reduce overhead.

FIGS. 16-19 illustrate embodiment f-OFDM configurations. In those figures, transmission time interval parameters are designated as “TTI,” sub-carrier spacing parameters are designated as “SC,” total symbol duration parameters are designated as “T,” and symbol overhead due to cyclic prefix, cyclic suffix or zero tails is designated as “O.” FIG. 16 illustrates a different frame structure on different f-OFDM sub-bands, and a same frame structure within a f-OFDM sub-band, according to an embodiment. FIG. 17 illustrates a different frame structure on different f-OFDM sub-bands, and different TTI lengths within a f-OFDM sub-band, according to an embodiment. The sub-carrier spacing, total symbol duration and symbol overhead, however, are the same within a f-OFDM sub-band. FIG. 18 illustrates different frame structures on different f-OFDM sub-bands, and different TTI lengths and symbol overhead within a f-OFDM sub-band, according to an embodiment. For example, this example may use zero-tail DFT-s-OFDM or adjustable zero-tail DFT-s-OFDM to provide the different symbol overhead. FIG. 19 illustrates a backward compatible extension (LTE frame structures), according to an embodiment. This may include normal and extended CP frame structures on different f-OFDM sub-bands occurring simultaneously.

FIG. 20 illustrates an example of an intra-f-OFDM adaptive TTI configuration, according to an embodiment. In this embodiment, a set of mappings (patterns) of logical TTI resources to physical TTI resources in a time duration (e.g., a radio frame of 10 ms) is defined. Mapping can be changed from frame to fame (e.g., by cycling through a predefined set of mappings or by signaling. The mapping can be of localized or distributed types. With localized TTI mapping, a TTI length occupies physical resources in the same bandwidth for the duration of a frame. With distributed TTI mapping, different TTI lengths can hop across the entire bandwidth as shown in FIG. 20. This allows for the exploitation of frequency diversity.

In accordance with an embodiment, a method for transmitting signals in a wireless network is provided. In this example, the method includes transmitting a first filtered-orthogonal frequency division multiplexing (f-OFDM) signal, and transmitting a second f-OFDM signal. The first f-OFDM signal and the second f-OFDM signal are communicated in accordance with different sub-carrier spacings than one another. The first f-OFDM signal and the second f-OFDM signal may carry symbols having different cyclic prefix (CP) lengths than one another. The first f-OFDM signal and the second f-OFDM signal may be transmitted over the same frequency sub-band during different transmission time intervals (TTIs). The first f-OFDM signal and the second f-OFDM signal may be transmitted over different frequency sub-bands during the same time period.

The method may further comprise assigning a first frame format to the first f-OFDM signal and a second frame format to the second f-OFDM signal. The first frame format may require a different CP length and a different sub-carrier spacing than the second frame format. In an embodiment, assigning the first frame format to the first f-OFDM signal comprises selecting the first frame format based on a characteristic of data to be carried by the first f-OFDM signal. The characteristic of the data to be carried by the first f-OFDM signal may comprise a latency requirement, a delay tolerance requirement, a traffic type, a service type, or a combination thereof. In another embodiment, assigning the first frame format to the first f-OFDM signal comprises selecting the first frame format based on a characteristic of a wireless channel over which the first f-OFDM signal is to be transmitted. The characteristic of the wireless channel comprises a multipath delay of the wireless channel. In yet another embodiment, assigning the first frame format to the first f-OFDM signal comprises selecting the first frame format based on a serving region size of the transmitter. In yet another embodiment, assigning the first frame format to the comprises selecting the first frame format based on a characteristic of a receiver associated with the first f-OFDM signal. The characteristic of the receiver associated with the first f-OFDM signal may comprise a mobility speed of the receiver.

In an embodiment, the first f-OFDM signal and the second f-OFDM signal are received by a receiver. The first f-OFDM signal may be communicated in accordance with a default frame format that is known by the receiver. The first f-OFDM signal may indicate that the second f-OFDM signal will be communicated in accordance with a frame format that is different than the default frame format.

In accordance with another embodiment, a method for receiving signals in a wireless network is provided. In this example, the method includes receiving a first filtered-orthogonal frequency division multiplexing (f-OFDM) signal, and receiving a second f-OFDM signal. The first f-OFDM signal and the second f-OFDM signal are communicated in accordance with different sub-carrier spacings than one another. The first f-OFDM signal and the second f-OFDM signal may carry symbols having different cyclic prefix (CP) lengths than one another. The first f-OFDM signal and the second f-OFDM signal may be received over the same frequency sub-band during different transmission time intervals (TTIs). The first f-OFDM signal and the second f-OFDM signal may be received over different frequency sub-bands during the same time period. The first f-OFDM may be communicated in accordance with a default frame format that is known by the receiver, and the first f-OFDM signal may indicate that the second f-OFDM signal will be communicated in accordance with a frame format that is different than the default frame format.

FIG. 21 illustrates a block diagram of an embodiment processing system 2100 for performing methods described herein, which may be installed in a host device. As shown, the processing system 2100 includes a processor 2104, a memory 2106, and interfaces 2110-2114, which may (or may not) be arranged as shown in FIG. 21. The processor 2104 may be any component or collection of components adapted to perform computations and/or other processing related tasks, and the memory 2106 may be any component or collection of components adapted to store programming and/or instructions for execution by the processor 1504. In an embodiment, the memory 2106 includes a non-transitory computer readable medium. The interfaces 2110, 2112, 2114 may be any component or collection of components that allow the processing system 2100 to communicate with other devices/components and/or a user. For example, one or more of the interfaces 2110, 2112, 2114 may be adapted to communicate data, control, or management messages from the processor 2104 to applications installed on the host device and/or a remote device. As another example, one or more of the interfaces 2110, 2112, 2114 may be adapted to allow a user or user device (e.g., personal computer (PC), etc.) to interact/communicate with the processing system 2100. The processing system 2100 may include additional components not depicted in FIG. 21, such as long term storage (e.g., non-volatile memory, etc.).

In some embodiments, the processing system 2100 is included in a network device that is accessing, or part otherwise of, a telecommunications network. In one example, the processing system 2100 is in a network-side device in a wireless or wireline telecommunications network, such as a base station, a relay station, a scheduler, a controller, a gateway, a router, an applications server, or any other device in the telecommunications network. In other embodiments, the processing system 2100 is in a user-side mobile device accessing a wireless or wireline telecommunications network, such as a mobile station, a user equipment (UE), a personal computer (PC), a tablet, a wearable communications device (e.g., a smartwatch, etc.), or any other device adapted to access a telecommunications network.

In some embodiments, one or more of the interfaces 2110, 2112, 2114 connects the processing system 2100 to a transceiver adapted to transmit and receive signaling over the telecommunications network. FIG. 22 illustrates a block diagram of a transceiver 2200 adapted to transmit and receive signaling over a telecommunications network. The transceiver 2200 may be installed in a host device. As shown, the transceiver 2200 comprises a network-side interface 2202, a coupler 2204, a transmitter 2206, a receiver 2208, a signal processor 2210, and a device-side interface 2212. The network-side interface 2202 may include any component or collection of components adapted to transmit or receive signaling over a wireless or wireline telecommunications network. The coupler 2204 may include any component or collection of components adapted to facilitate bi-directional communication over the network-side interface 2202. The transmitter 2206 may include any component or collection of components (e.g., up-converter, power amplifier, etc.) adapted to convert a baseband signal into a modulated carrier signal suitable for transmission over the network-side interface 2202. The receiver 2208 may include any component or collection of components (e.g., down-converter, low noise amplifier, etc.) adapted to convert a carrier signal received over the network-side interface 2202 into a baseband signal. The signal processor 2210 may include any component or collection of components adapted to convert a baseband signal into a data signal suitable for communication over the device-side interface(s) 2212, or vice-versa. The device-side interface(s) 2212 may include any component or collection of components adapted to communicate data-signals between the signal processor 2210 and components within the host device (e.g., the processing system 2100, local area network (LAN) ports, etc.).

The transceiver 2200 may transmit and receive signaling over any type of communications medium. In some embodiments, the transceiver 2200 transmits and receives signaling over a wireless medium. For example, the transceiver 2200 may be a wireless transceiver adapted to communicate in accordance with a wireless telecommunications protocol, such as a cellular protocol (e.g., long-term evolution (LTE), etc.), a wireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or any other type of wireless protocol (e.g., Bluetooth, near field communication (NFC), etc.). In such embodiments, the network-side interface 2202 comprises one or more antenna/radiating elements. For example, the network-side interface 2202 may include a single antenna, multiple separate antennas, or a multi-antenna array configured for multi-layer communication, e.g., single input multiple output (SIMO), multiple input single output (MISO), multiple input multiple output (MIMO), etc. In other embodiments, the transceiver 2200 transmits and receives signaling over a wireline medium, e.g., twisted-pair cable, coaxial cable, optical fiber, etc. Specific processing systems and/or transceivers may utilize all of the components shown, or only a subset of the components, and levels of integration may vary from device to device.

While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments. 

What is claimed is:
 1. A method for transmitting signals in a wireless network, the method comprising: transmitting, by a transmitter, a first filtered-orthogonal frequency division multiplexing (f-OFDM) signal; and transmitting, by the transmitter, a second f-OFDM signal, the first f-OFDM signal and the second f-OFDM signal being communicated in accordance with different sub-carrier spacings than one another.
 2. The method of claim 1, wherein the first f-OFDM signal and the second f-OFDM signal carry symbols having different cyclic prefix (CP) lengths than one another.
 3. The method of claim 1, wherein the first f-OFDM signal and the second f-OFDM signal are transmitted over the same frequency sub-band during different transmission time intervals (TTIs).
 4. The method of claim 1, wherein the first f-OFDM signal and the second f-OFDM signal are transmitted over different frequency sub-bands during the same time period.
 5. The method of claim 1, further comprising assigning a first frame format to the first f-OFDM signal and a second frame format to the second f-OFDM signal, wherein the first frame format requires a different CP length and a different sub-carrier spacing than the second frame format.
 6. The method of claim 5, wherein assigning the first frame format to the first f-OFDM signal comprises: selecting the first frame format based on a characteristic of data to be carried by the first f-OFDM signal.
 7. The method of claim 6, wherein the characteristic of the data to be carried by the first f-OFDM signal comprises a latency requirement, a delay tolerance requirement, a traffic type, a service type, or a combination thereof.
 8. The method of claim 5, wherein assigning the first frame format to the first f-OFDM signal comprises: selecting the first frame format based on a characteristic of a wireless channel over which the first f-OFDM signal is to be transmitted.
 9. The method of claim 8, wherein the characteristic of the wireless channel comprises a multipath delay of the wireless channel.
 10. The method of claim 5, wherein assigning the first frame format to the first f-OFDM signal comprises: selecting the first frame format based on a serving region size of the transmitter.
 11. The method of claim 5, wherein assigning the first frame format to the first f-OFDM signal comprises: selecting the first frame format based on a characteristic of a receiver associated with the first f-OFDM signal.
 12. The method of claim 11, wherein the characteristic of the receiver associated with the first f-OFDM signal comprises a mobility speed of the receiver.
 13. The method of claim 1, wherein the first f-OFDM signal and the second f-OFDM signal are received by a receiver, the first f-OFDM signal being communicated in accordance with a default frame format that is known by the receiver, and wherein the first f-OFDM signal indicates that the second f-OFDM signal will be communicated in accordance with a frame format that is different than the default frame format.
 14. A transmitter comprising: a processor; and a computer readable storage medium storing programming for execution by the processor, the programming including instructions to: transmit a first filtered-orthogonal frequency division multiplexing (f-OFDM) signal; and transmit a second f-OFDM signal, the first f-OFDM signal and the second f-OFDM signal being communicated in accordance with different sub-carrier spacings than one another.
 15. The transmitter of claim 14, wherein the first f-OFDM signal and the second f-OFDM signal carry symbols having different cyclic prefix (CP) lengths than one another.
 16. The transmitter of claim 14, wherein the first f-OFDM signal and the second f-OFDM signal are transmitted over the same frequency sub-band during different transmission time intervals (TTIs).
 17. The transmitter of claim 14, wherein the first f-OFDM signal and the second f-OFDM signal are transmitted over different frequency sub-bands during the same time period.
 18. A method for receiving signals in a wireless network, the method comprising: receiving, by a receiver, a first filtered-orthogonal frequency division multiplexing (f-OFDM) signal; and receiving, by the receiver, a second f-OFDM signal, the first f-OFDM signal and the second f-OFDM signal being communicated in accordance with different sub-carrier spacings than one another.
 19. The method of claim 18, wherein the first f-OFDM signal and the second f-OFDM signal carry symbols having different cyclic prefix (CP) lengths than one another.
 20. The method of claim 18, wherein the first f-OFDM signal and the second f-OFDM signal are received over the same frequency sub-band during different transmission time intervals (TTIs).
 21. The method of claim 18, wherein the first f-OFDM signal and the second f-OFDM signal are received over different frequency sub-bands during the same time period.
 22. The method of claim 18, wherein the first f-OFDM is communicated in accordance with a default frame format that is known by the receiver, and wherein the first f-OFDM signal indicates that the second f-OFDM signal will be communicated in accordance with a frame format that is different than the default frame format.
 23. A receiver comprising: a processor; and a computer readable storage medium storing programming for execution by the processor, the programming including instructions to: receive a first filtered-orthogonal frequency division multiplexing (f-OFDM) signal; and receive a second f-OFDM signal, the first f-OFDM signal and the second f-OFDM signal being communicated in accordance with different sub-carrier spacings than one another.
 24. The receiver of claim 23, wherein the first f-OFDM signal and the second f-OFDM signal carry symbols having different cyclic prefix (CP) lengths than one another.
 25. The receiver of claim 23, wherein the first f-OFDM signal and the second f-OFDM signal are received over the same frequency sub-band during different transmission time intervals (TTIs).
 26. The receiver of claim 23, wherein the first f-OFDM signal and the second f-OFDM signal are received over different frequency sub-bands during the same time period. 